The Lady of the Lake or Dame du Lac is a title that was held by more than one woman. Generally she is regarded as the water-fay that raised Sir Lancelot beneath the murky waters of her lake. However, she is best known as the one who, at the request of Merlin, presented the magical sword Excalibur to Arthur.
In the Vulgate Cycle, the Lady of the Lake rears and protects Sir Lancelot as well as the brothers, Sir Bors (Bohort) and Sir Lionel - sons of King Bohort (Bors) of Gaunes. She is often given the name Nimue or variations such as Niniane and Vivien. However, Malory uses Nyneve (Nimue) as well as an un-named Lady of the Lake.
This un-named water-fay is killed by Sir Balin resulting from a feud between the two. Other authors have also treated some of these names (Nimue, Vivien, etc) as separate 'Lady of the Lake' characters. For example, Tennyson portrays Viviane as a deceitful person who ensnares Merlin, yet depicts the Lady of the Lake as the compassionate character who raises Sir Lancelot and presents Arthur with his magical sword. So, it is clear that the name has been applied to a few different women.
The Lake and AvalonEdit
Nyneve (or Nimue) is, at the end of Malory's Le Morte d'Arthur the chief Lady of the Lake. She is one of the queens who take Arthur to Avalon after he has been grievously wounded at the battle of Camlann. Thus, Avalon has been sometimes associated with the realm of the Lady of the Lake in some literary traditions. Since Morgan le Fay in some sources replaced Nimue as Merlin's student in exchange for offering her love to the wizard, and is also one of the queens that take Arthur to Avalon, she is sometimes also considered a Lady of the Lake.